RESUMEN
In Ecuador, a national program for bovine brucellosis control has been in implementation since 2008. Given the costs, small- and medium-sized livestock holders are not completely committed to it. The objective of this study was to determine true prevalence (TP) of bovine brucellosis in small- and medium-sized herd populations, as well as the diagnostic sensitivity and specificity of the Rose Bengal (RB) test and the sero-agglutination test (SAT)-EDTA using a Bayesian approach. Between 2011 and 2016, 2733 cattle herds were visited, and 22,592 animal blood samples were taken in nineteen provinces on mainland Ecuador. Bayes-p and deviance information criterion (DIC) statistics were used to select models. Additionally, risk-factor analysis was used for herds according to their brucellosis test status. True prevalence (TP) in herds was estimated by pool testing. National seroprevalence of farms was 7.9% (95% CI: 6.79-9.03), and TP was 12.2% (95% CI: 7.8-17.9). Apparent prevalence (AP) in animals was 2.2% (95% CI: 1.82-2.67), and TP was 1.6% (95% CrI: 1.0-2.4). Similarly, the sensitivity of the RB was estimated at 64.6% (95% CrI: 42.6-85.3) and specificity at 98.9% (95% CrI: 98.6-99.0); for the SAT-EDTA test, sensitivity was 62.3% (95% CrI: 40.0-84.8) and 98.9% (95% CrI: 98.6-99.1) for specificity. Results of the two tests were highly correlated in infected and uninfected animals. Likewise, high spatial variation was observed, with the Coastal Region being the zone with the highest TP at 2.5%. (95% CrI: 1.3-3.8%) in individual animals and 28.2% (95% CI: 15.7-39.8) in herds. Risk factors include herd size, type of production (milk, beef, and mixed), abortions recorded, and vaccination. The results of this study serve to guide authorities to make decisions based on parallel testing at the beginning of a bovine brucellosis program for small livestock holders to increase sensitivity level of the screening tests in Ecuador.
RESUMEN
The province of Santo Domingo de los Tsáchilas in Ecuador is a strategic place for cattle production and trade. The lack of knowledge about tick species, tick control and tick-borne diseases in Ecuador prompted this study with the goal of identifying the cattle-tick species and tick-borne agents present in the area and molecularly determining the potential acaricide resistance to amitraz of the major cattle tick species. Eighty-four cattle farms were visited and in 88 % of them, cattle were infested with ticks. Additionally, 24 historical samples from other surrounding Ecuadorian provinces, were screened as well. Besides morphological keys, PCR-RFLP MspI was used to confirm the presence of the Rhipicephalus ticks. The tick samples were also screened for tick-borne agents using PCR-RFLP BseDI and Hhal tests to identify circulating Babesia sp. and Anaplasma spp. Furthermore, the PCR-RFLP EciI technique was used to identify the amitraz resistance gene in populations of Rhipicephalus microplus in the province. Pooled testing was used to determine prevalence at individual-tick level. The presence of R. microplus and Amblyomma cajennense sensu lato (s.l.) ticks was found in 83 % and 21 % of the cattle farms respectively, showing R. microplus is widespread in the province of Santo Domingo de los Tsáchilas. Regarding tick-borne agents, only Anaplasma marginale was observed in 50 % of the visited farms of the province, while about 27 % of the ticks tested positive according to estimations from the data of the tick pools. The presence of Babesia bigemina was only confirmed in samples collected outside the province. The amitraz resistance allele in R. microplus was found in 62 % of the farms, but the percentage of farms with cattle ticks completely resistant to this acaricide was low (2%). The findings of this study should prompt cattle producers and animal health authorities to monitor control strategies, which address the management of resistant tick populations and the epidemiologically-unstable areas of tick-borne diseases.
Asunto(s)
Acaricidas/farmacología , Enfermedades de los Bovinos/epidemiología , Resistencia a Medicamentos , Ixodidae , Infestaciones por Garrapatas/veterinaria , Toluidinas/farmacología , Anaplasma/aislamiento & purificación , Animales , Babesia/aislamiento & purificación , Bovinos , Enfermedades de los Bovinos/parasitología , Ecuador/epidemiología , Femenino , Ixodidae/efectos de los fármacos , Ixodidae/microbiología , Ixodidae/parasitología , Larva/efectos de los fármacos , Larva/microbiología , Larva/parasitología , Masculino , Ninfa/efectos de los fármacos , Ninfa/microbiología , Ninfa/parasitología , Especificidad de la Especie , Infestaciones por Garrapatas/epidemiología , Infestaciones por Garrapatas/parasitologíaRESUMEN
Brucellosis is an important but neglected zoonosis that causes serious economic losses both in livestock and human populations. The aim of the present study was to estimate the true prevalence of brucellosis together with diagnostic sensitivity and specificity of three serological tests in humans of the northwestern part of Ecuador using a Bayesian approach adjusted for the dependencies among the multiple tests to avoid any misinterpretation. In addition, the causal agent responsible for human brucellosis was also identified. Using a total of 3,733 samples collected from humans in this area between 2006 and 2008, the prevalence of human brucellosis and the diagnostic test characteristics of the Rose Bengal fast agglutination test (RBT), Wright's slow agglutination test with ethylenediaminetetraacetic acid disodium salt dehydrate (EDTA) (SAT-EDTA), and indirect ELISA (iELISA) were estimated using a Bayesian approach. The estimated true prevalence of human brucellosis was 1% (credibility interval: 0.4-1.6). The sensitivities of iELISA and RBT were higher than and similar (95.1% and 95.0%, respectively) to those of SAT-EDTA (60.8%). Even though all tests indicated a high specificity (> 99.0%), the specificity of SAT-EDTA was highest (99.9%). The circulating strain in this study area was identified to be Brucella abortus biotype 4 based on culture and microbiological characterization. The RBT and the iELISA are recommended for estimating the true prevalence of human brucellosis and/or for surveillance programs following their high sensitivities and specificities. The proposed strategy supports evidence-based medicine for clinicians and policy-makers to ensure appropriate preventive and control program of brucellosis worldwide.
Asunto(s)
Pruebas de Aglutinación/normas , Anticuerpos Antibacterianos/sangre , Brucella abortus/aislamiento & purificación , Brucelosis/diagnóstico , Brucelosis/epidemiología , Ensayo de Inmunoadsorción Enzimática/normas , Adolescente , Adulto , Anciano , Animales , Teorema de Bayes , Brucella abortus/inmunología , Brucelosis/microbiología , Brucelosis/transmisión , Bovinos , Estudios Transversales , Ecuador/epidemiología , Ácido Edético/química , Monitoreo Epidemiológico , Femenino , Humanos , Masculino , Persona de Mediana Edad , Prevalencia , Rosa Bengala/química , Sensibilidad y EspecificidadRESUMEN
Very few, mostly old, and only preliminary serological studies of brucellosis in goats exist in Ecuador. In order to assess the current epidemiological situation, we performed a cross-sectional serological study in the goat populations of Carchi (n = 160 animals), Pichincha (n = 224 animals), and Loja provinces (n = 2024 animals). Only two positive serological results (RB negative and SAT-EDTA ≥400 IU/ml) were obtained in lactating goats from the same farm in Quito (Pichincha province). Additionally, milk was sampled from 220 animals in Pichincha province. The present study indicates a low apparent prevalence in Pichincha province and absence in Carchi and Loja provinces. A total of 25 positive milk ring tests (MRT) were obtained in Pichincha province yielding a prevalence of MRT of 11.16%. Subsequent culture was performed on the positive MRT samples. All results were negative, apart from a single sample, obtained from a serologically positive goat in Quito, that was positive for Brucella abortus strain 19 (B19). Several hypotheses are forwarded concerning this unexpected result. The most likely hypothesis is the possible accidental use of a needle, previously used for vaccination of cattle with the said vaccine, for the administration of drug treatment to the goat. This hypothesis underlines the necessity of biosecurity measures to prevent this type of accidents.
Asunto(s)
Anticuerpos Antibacterianos/sangre , Brucella abortus/inmunología , Brucelosis/veterinaria , Enfermedades de las Cabras/epidemiología , Animales , Brucelosis/epidemiología , Estudios Transversales , Ecuador/epidemiología , Femenino , Abastecimiento de Alimentos , Enfermedades de las Cabras/sangre , Enfermedades de las Cabras/prevención & control , Cabras , Lactancia , Leche/microbiología , PrevalenciaRESUMEN
BACKGROUND: Epilepsy is one of the most common signs of Neurocysticercosis (NCC). In this study, spatial and temporal variations in the incidence of hospitalized cases (IHC) of epilepsy and NCC in Ecuadorian municipalities were analyzed. Additionally, potential socio-economic and landscape indicators were evaluated in order to understand in part the macro-epidemiology of the Taenia solium taeniasis/cysticercosis complex. METHODOLOGY: Data on the number of hospitalized epilepsy and NCC cases by municipality of residence were obtained from morbidity-hospital systems in Ecuador. SatScan software was used to determine whether variations in the IHC of epilepsy and NCC in space and time. In addition, several socio-economic and landscape variables at municipality level were used to study factors intervening in the macro-epidemiology of these diseases. Negative Binomial regression models through stepwise selection and Bayesian Model Averaging (BMA) were used to explain the variations in the IHC of epilepsy and NCC. PRINCIPAL FINDINGS: Different clusters were identified through space and time. Traditional endemic zones for NCC and epilepsy, recognized in other studies were confirmed in our study. However, for both disorders more recent clusters were identified. Among municipalities, an increasing tendency for IHC of epilepsy, and a decreasing tendency for the IHC of NCC were observed over time. In contrast, within municipalities a positive linear relationship between both disorders was found. An increase in the implementation of systems for eliminating excrements would help to reduce the IHC of epilepsy by 1.00% (IC95%; 0.2%-1.8%) and by 5.12% (IC95%; 3.63%-6.59%) for the IHC of NCC. The presence of pig production was related to IHC of NCC. CONCLUSION/SIGNIFICANCE: Both disorders were related to the lack of an efficient system for eliminating excrements. Given the appearance of recent epilepsy clusters, these locations should be studied in depth to discriminate epilepsies due to NCC from epilepsies due to other causes. Field studies are needed to evaluate the true prevalence of cysticercosis in humans and pigs in different zones of the country in order to better implement and manage prevention and/or control campaigns.
Asunto(s)
Epilepsia/epidemiología , Epilepsia/etiología , Neurocisticercosis/epidemiología , Topografía Médica , Ecuador/epidemiología , Exposición a Riesgos Ambientales , Hospitalización , Humanos , Incidencia , Prevalencia , Factores de Riesgo , Factores Socioeconómicos , Análisis Espacio-TemporalRESUMEN
BACKGROUND: Focal screening and treatment (FSAT) of malaria infections has recently been introduced in Peru to overcome the inherent limitations of passive case detection (PCD) and further decrease the malaria burden. Here, we used a relatively straightforward mathematical model to assess the potential of FSAT as elimination strategy for Plasmodium falciparum malaria in the Peruvian Amazon Region. METHODS: A baseline model was developed to simulate a scenario with seasonal malaria transmission and the effect of PCD and treatment of symptomatic infections on the P. falciparum malaria transmission in a low endemic area of the Peruvian Amazon. The model was then adjusted to simulate intervention scenarios for predicting the long term additional impact of FSAT on P. falciparum malaria prevalence and incidence. Model parameterization was done using data from a cohort study in a rural Amazonian community as well as published transmission parameters from previous studies in similar areas. The effect of FSAT timing and frequency, using either microscopy or a supposed field PCR, was assessed on both predicted incidence and prevalence rates. RESULTS: The intervention model indicated that the addition of FSAT to PCD significantly reduced the predicted P. falciparum incidence and prevalence. The strongest reduction was observed when three consecutive FSAT were implemented at the beginning of the low transmission season, and if malaria diagnosis was done with PCR. Repeated interventions for consecutive years (10 years with microscopy or 5 years with PCR), would allow reaching near to zero incidence and prevalence rates. CONCLUSIONS: The addition of FSAT interventions to PCD may enable to reach P. falciparum elimination levels in low endemic areas of the Amazon Region, yet the progression rates to those levels may vary substantially according to the operational criteria used for the intervention.
Asunto(s)
Antimaláricos/uso terapéutico , Malaria Falciparum/prevención & control , Estudios de Cohortes , Femenino , Humanos , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/epidemiología , Malaria Falciparum/parasitología , Masculino , Modelos Teóricos , Perú/epidemiología , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/genética , Plasmodium falciparum/aislamiento & purificación , Plasmodium falciparum/fisiología , Población RuralRESUMEN
Human brucellosis in Ecuador is underreported and based only on passive surveillance. Since 2008, brucellosis was removed from the list of communicable diseases in the country. Until now, the true human brucellosis picture has not yet been determined. The aim of this study was to determine the seroprevalence of the disease, identify risk factors associated with brucellosis seropositivity in humans, and isolate circulating strains of Brucella spp. in the northwestern part of Ecuador. Between 2006 and 2008, a large transect survey was conducted, based on blood sampling of people from the northwestern part of Ecuador (n=3733) together with an epidemiological inquiry. On the basis of three diagnostic tests used in parallel, the overall seroprevalence was estimated as 1.88% (95% confidence interval [CI] 1.48-2.38). Based on a multivariable random effects logistic regression analysis, the main risk factors associated with human brucellosis seropositivity were contact with livestock (odds ratio [OR]=3.0; CI 1.25-7.08), consumption of fetus and placenta (OR=2.5; CI 1.18-5.22), and involvement in activities at risk for brucellosis infection (OR=1.8; CI 1.00-3.35). Noticeable variation in brucellosis seropositivity among humans within cantons was observed. The circulating strain was Brucella abortus biotype 4. This study emphasized that contact with livestock, consumption of fetus and placenta, and occupational hazard group were all significant risk factors for the transmission of brucellosis among individuals in the northwestern part of Ecuador. Alongside encouraging the launching of educational campaigns against brucellosis, especially in rural areas where 36% of the population lives, controlling this zoonotic disease in animals will directly benefit its prevention in humans, especially because there is no safe and efficacious vaccine against brucellosis in humans.
Asunto(s)
Brucelosis/epidemiología , Mataderos , Adolescente , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Animales , Niño , Preescolar , Ecuador/epidemiología , Femenino , Humanos , Ganado , Masculino , Productos de la Carne/microbiología , Productos de la Carne/estadística & datos numéricos , Persona de Mediana Edad , Leche/microbiología , Leche/estadística & datos numéricos , Exposición Profesional/estadística & datos numéricos , Embarazo , Factores de Riesgo , Estudios Seroepidemiológicos , Distribución por Sexo , Adulto JovenRESUMEN
This study aimed to determine whether variations in the incidence of reported cases of human brucellosis in Ecuador were clustered in space and time. In addition, the effects of cattle and small ruminant population density and other socio-economic factors on the incidence were investigated. Significant space-time clusters were found in the northern and southern highlands and parts of Ecuadorian Amazonia. Customs of people, cattle, goat and sheep population density appeared to influence the incidence of brucellosis. In this study, the incidence of reported cases of human brucellosis was found to be higher in the highlands (sierra) and in municipalities near Peru and Colombia. The results of this study highlight the need for prevention and control measures aimed at abating the incidence of brucellosis among livestock and humans.
Asunto(s)
Brucelosis/epidemiología , Animales , Bovinos , Análisis por Conglomerados , Ecuador/epidemiología , Cabras , Humanos , Incidencia , Distribución de Poisson , Densidad de Población , Análisis de Regresión , Ovinos , Análisis Espacio-Temporal , Zoonosis/epidemiologíaRESUMEN
AIMS: To present a new approach for estimating the "true prevalence" of malaria and apply it to datasets from Peru, Vietnam, and Cambodia. METHODS: Bayesian models were developed for estimating both the malaria prevalence using different diagnostic tests (microscopy, PCR & ELISA), without the need of a gold standard, and the tests' characteristics. Several sources of information, i.e. data, expert opinions and other sources of knowledge can be integrated into the model. This approach resulting in an optimal and harmonized estimate of malaria infection prevalence, with no conflict between the different sources of information, was tested on data from Peru, Vietnam and Cambodia. RESULTS: Malaria sero-prevalence was relatively low in all sites, with ELISA showing the highest estimates. The sensitivity of microscopy and ELISA were statistically lower in Vietnam than in the other sites. Similarly, the specificities of microscopy, ELISA and PCR were significantly lower in Vietnam than in the other sites. In Vietnam and Peru, microscopy was closer to the "true" estimate than the other 2 tests while as expected ELISA, with its lower specificity, usually overestimated the prevalence. CONCLUSIONS: Bayesian methods are useful for analyzing prevalence results when no gold standard diagnostic test is available. Though some results are expected, e.g. PCR more sensitive than microscopy, a standardized and context-independent quantification of the diagnostic tests' characteristics (sensitivity and specificity) and the underlying malaria prevalence may be useful for comparing different sites. Indeed, the use of a single diagnostic technique could strongly bias the prevalence estimation. This limitation can be circumvented by using a Bayesian framework taking into account the imperfect characteristics of the currently available diagnostic tests. As discussed in the paper, this approach may further support global malaria burden estimation initiatives.
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Malaria/diagnóstico , Malaria/epidemiología , Adolescente , Adulto , Teorema de Bayes , Cambodia/epidemiología , Niño , Preescolar , Diagnóstico Diferencial , Pruebas Diagnósticas de Rutina/normas , Pruebas Diagnósticas de Rutina/estadística & datos numéricos , Humanos , Lactante , Persona de Mediana Edad , Perú/epidemiología , Prevalencia , Sensibilidad y Especificidad , Vietnam/epidemiología , Adulto JovenRESUMEN
Taenia solium cysticercosis is an endemic zoonosis in many developing countries. Serological tests are the most appropriate diagnostic tools to understand the transmission dynamics of the parasite, but the performances of these methods in such a setting are not known. A south Ecuadorian human population living in an endemic area was tested using three common serological tests. Because none of them is a gold standard, a Bayesian Latent Class analysis was used to estimate the test characteristics. Two definitions of a case were considered to differentiate between prevalence of current infection and prior exposure to the parasite. Differences between the performances of the same test in function of the definition of a case were observed. This study shows that test results and prior information should be interpreted carefully in a Bayesian analysis framework, particularly when the latter is based on clinical studies.